The present invention relates to a vehicle rearview mirror assembly. In particular, the invention relates to a rearview mirror assembly for selectively positioning a vehicle interior rearview mirror, of the day/night type in either a full reflectance (day) mode or a partial reflectance (night) mode.
A number of day/night type interior rearview mirror assemblies are known. These mirror assemblies generally utilize a prism type reflecting mirror which is adapted to be selectively moved into the day and night reflecting modes. During travel at night, with the rearview mirror in the partial reflectance (night) mode, glare from the headlights of a following vehicle is substantially reduced and is not troublesome to the driver of the vehicle.
However, problems with the known types of day/night interior rearview mirror assemblies include undesirable vibration and noise characteristics, small tolerance limits, high manufacturing cost and are complicated due to a multiplicity of parts.
More specifically, GENTEX European Pat. No. 67,335 describes a rearview assembly in which an eccentric cam and cam follower arrangement is used to move a prism mirror between full and partial reflectance modes. A unidirectional electric motor powered from the vehicle battery is provided as the power source to rotate the eccentric cam. This construction has a number of disadvantages. First, as the eccentric cam is driven only in one direction there is no defined stopping point for the cam and thus accurate positioning of the mirror in either the full reflectance or partial reflectance modes is dependent on the stopping control of the motor. However, since it is known that the voltage output of the vehicle electrical system varies between about 9 to 16 V, then the power output of the motor can vary thus causing over-run or under-run of the eccentric cam resulting in inaccurate positioning of the mirror. In addition, since the eccentric cam and cam follower arrangement have to operate within the vehicle temperature specification range which is usually -40.degree. to +90.degree. C., a substantial variation in frictional resistance between the eccentric cam and cam follower can also result in under-run or over-run of the eccentric cam thus producing inaccurate positioning of the mirror.
Thus, it is an object of the present invention to provide a day/night type rearview mirror assembly, that is selectively positioned in a full reflectance (day) mode or a partial refelctance (night) mode, that is simple in construction and which substantially mitigates the above mentioned problems.